CN114806695A

CN114806695A - Method for treating and recycling waste cutting fluid

Info

Publication number: CN114806695A
Application number: CN202210469219.0A
Authority: CN
Inventors: 张鸿; 周峥
Original assignee: Luxcase Precision Technology Yancheng Co Ltd
Current assignee: Luxcase Precision Technology Yancheng Co Ltd
Priority date: 2022-04-30
Filing date: 2022-04-30
Publication date: 2022-07-29
Anticipated expiration: 2042-04-30
Also published as: CN114806695B

Abstract

The invention discloses a method for treating and recycling waste cutting fluid. The cutting fluid adjusting back comprises the following steps: s1, pretreatment; s2, filtering and separating; s3, adjusting back the cutting fluid; and preparing a plurality of kinds of concentrated solutions from the lost components, triggering a plurality of external concentrated solution valves through the PLC, adding corresponding concentrated solutions, and obtaining the new cutting fluid prepared by callback. According to the invention, a new regeneration liquid is formed by adding the concentrated solution for callback, and meanwhile, the separated water can be recycled on line, so that the method can be used for cutting fluid dilution or other water using scenes.

Description

Method for treating and recycling waste cutting fluid

Technical Field

The invention belongs to the field of wastewater treatment, and particularly relates to a method for treating and recycling waste cutting fluid.

Background

CNC technology has found widespread use in the metal working industry since its invention in 1950. The cutting fluid plays roles of rust prevention (preventing equipment from rusting, preventing internal clamps from rusting and preventing a workpiece from rusting) -7 series aluminum alloy is easy to oxidize in air), cooling, lubricating, cleaning and chip removal in the machining process, wherein the water-based cutting fluid and the semisynthetic cutting fluid are good in cooling effect, safe to use and low in cost, and become a mainstream cooling mode for cutting.

However, the cutting fluid inevitably contains impurities such as metal particles (chips), dust, guide oil, etc. during use, and the use of these impurities at a high content may damage the tool and the surface to be machined. And the impurities are main catalysts for oxidation deterioration of the cutting fluid, and can accelerate chemical changes of the cutting fluid to cause higher acidity and larger interfacial tension, so that the cutting fluid is deteriorated and disabled, and a large amount of waste cutting fluid is generated.

Meanwhile, the CNC machine table is provided with an air exhaust pipeline, and oil mist waste gas is introduced into the purification tower through an air pipe. After passing through the filler layer, the oil mist is fully contacted with the water mist liquid, more than 80% of the oil mist is purified and dissolved in water, and the waste gas after the oil mist purification is removed by the dehydration of the plate and then is discharged into the atmosphere by the fan. The water is pumped to the top of the tower by a water pump at the bottom of the tower and sprayed downwards, and then the water is recycled to the bottom of the tower and pumped to the top of the tower by the water pump for the next cycle. Usually 50-100 CNC machines are equipped with an oil mist washing tower, and each plant area generates more than 60 tons of washing wastewater per day according to the number of configured CNC machines. Furthermore, in the field, when the floor is cleaned by the cleaning machine, a large amount of the cutting fluid-containing washing water and the washing machine water is generated daily.

The cutting fluid belongs to dangerous waste and needs a professional company with recovery qualification to be treated, which is very costly. But wherein a large number of useful components are of value for recovery. Taking the waste liquid of the purification tower with the lowest concentration as an example, about 5-15% of the effective cutting fluid components still exist, and the concentration proportion of other waste cutting fluids is higher. Therefore, how to recycle the wastes and turn the wastes into valuables is a problem which needs to be solved urgently.

Disclosure of Invention

In view of the above technical problems, the present invention provides a method for treating and recycling waste cutting fluid, which adopts the following technical scheme:

a method for treating and recycling waste cutting fluid comprises the following steps:

s1, pretreatment;

s2, filtering and separating to enrich the components of the cutting fluid and obtain pure water;

s3, adjusting back the cutting fluid;

the S3 cutting fluid is adjusted back, and the method comprises the following steps:

s31, dividing the lost components in the waste cutting fluid into oil and additive;

it will be appreciated by those skilled in the art that the missing components, which are typically oils and additives, can be determined by comparing the spent cutting fluid to the original cutting fluid in a modest manner, and the specific species missing can be known, for example, by performing a comparative analysis of the composition using HPLC-GC-MS.

S32, detecting the refractive index and the density of the waste cutting fluid and the original cutting fluid by taking the refractive index and the density as actual detection indexes; respectively drawing two influence curves;

s33, collecting and comparing, monitoring the density and the refractivity of the waste cutting fluid in real time, comparing and calculating the density and the refractivity of the waste cutting fluid with those of the original cutting fluid, and calculating the lost components and the content of the concentrated solution to be added according to the two influence curve results of S32;

s34, triggering a plurality of external concentrated solution valves by a PLC (programmable logic controller), adding corresponding concentrated solution, wherein the adding mode is based on a calculated theoretical value A1, the adding amount is 70% of the theoretical value A1, then detecting the density and the refractive index, obtaining a theoretical value A2 needing to be added after comparing and fitting with a curve, and adding 70% of the theoretical value A2 again, so that the method gradually approaches to the situation that the density and the refractive index stop within an error range of 2% of the initial values, and obtaining the regenerated solution.

In one embodiment, the pretreatment in S1 includes oil removal, slag removal, decolorization, and sterilization.

In one embodiment, the filtering separation in S2 includes an electro-adsorption desalination separation.

In one embodiment, the filtration and separation in S2 includes sequentially performing a first-stage nano-membrane, a second-stage laminated molecular deposition membrane, and a third-stage reverse osmosis membrane filtration.

In one embodiment, the molecular weight of the organic substance intercepted by the primary nano-membrane is 150-500 g/mol.

In one embodiment, the tertiary reverse osmosis membrane blocks dissolved inorganic molecules as well as organics having a relative molecular mass greater than 100 g/mol.

In one embodiment, the filtering and separating in S2 includes performing at least one of UF ultrafiltration, electro-adsorption, and electrodialysis.

In one embodiment, the filtering and separating in S2 includes performing at least one of carbon filtration, sand filtration, polytetrafluoroethylene evaporator evaporation, and MVR low pressure evaporation (mechanical vapor compression).

The invention adopts electric adsorption, has low water production cost, simple process flow, low energy consumption, long service life, no maintenance, high water utilization rate, wide application range, stable core equipment performance, strong tolerance, adaptability to different water qualities and loose water inlet condition.

The method for treating and recycling the waste cutting fluid is simple, dynamic adjustment can be carried out in a mode of detecting the refractivity and the density of the waste cutting fluid and the original cutting fluid by taking the refractivity and the density as actual detection indexes until the waste cutting fluid is changed into the useful cutting fluid through component adjustment back, and the step is almost obviously different from the original cutting fluid, so that waste is changed into valuable.

Drawings

FIG. 1 is a flow chart showing the steps of a method for treating and recycling a waste cutting fluid according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a system corresponding to the method for treating and recycling waste cutting fluid according to the embodiment of the present invention;

FIG. 3 is a schematic view of a laminated filter in a method for treating and recycling a waste cutting fluid according to an embodiment of the present invention;

FIG. 4 is a graph showing the relationship between density and loss ratio of cutting fluid and concentrate according to an embodiment of the present invention;

FIG. 5 is a graph showing the relationship between the refractive index and the loss ratio of the cutting fluid and the concentrated fluid in the embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1 to 5, the present invention discloses a method for treating and recycling waste cutting fluid, comprising the steps of:

s1, pretreatment;

wherein, the pretreatment of S1 includes oil removal, slag removal, decoloration and sterilization, the liquid taken from the stock solution tank 10 is firstly discharged into the pretreatment tank 20 for oil removal and slag removal, and is sterilized by UV and the like, the anaerobic bacteria in the liquid are removed, and the preliminary purification is carried out. Wherein an oil-water separation filter is adopted to separate surface floating oil, residue in a system is removed by filtration, activated carbon is used for decoloring waste liquid, and a UV lamp or a bactericide is added for sterilizing the waste liquid.

S2, filtering and separating;

the S2 filtration separation is specifically electro-adsorption desalination separation, which is a novel water treatment TECHNOLOGY beginning to rise in the late 90 th century, namely electro-adsorption TECHNOLOGY (EST), also called capacitive desalination TECHNOLOGY. The basic principle is based on the theory of electric double layers in electrochemistry, and the purposes of removing charged particles in water, decomposing organic matters and the like are realized by utilizing the electrochemical characteristics of the surface of a charged electrode. When raw water flows between the anode and the cathode, charged particles in the water migrate to the electrodes with opposite charges respectively, are adsorbed by the electrodes and are stored in the double-electrode layer, and the charged particles are enriched and concentrated on the surfaces of the electrodes to finally realize the separation from the water. In one embodiment, the filtering separation in S2 includes an electro-adsorption desalination separation.

In one embodiment, the three-stage reverse osmosis membrane blocks all dissolved inorganic molecules as well as organics having a relative molecular mass greater than 100 g/mol.

In another embodiment, the S2 filtration separation includes a first-stage nanomembrane, a second-stage laminated molecular deposition membrane, and a third-stage reverse osmosis membrane arranged in this way, which is the multi-stage membrane linkage structure 30.

The molecular weight of the first-level nano-membrane for intercepting organic matters is 150-500g/mol, the capacity for intercepting soluble salt is 2-98%, and large organic molecules and suspended matters in water are removed.

In the secondary laminated molecular deposition film, when the laminated filter works normally, water flows through the laminated sheets, impurities are gathered and intercepted by the sheet walls and the grooves, and the composite inner section of the sheet groove provides three-dimensional filtration similar to that generated in the sandstone filter to remove heavy metal ions.

Referring to fig. 3, which is a schematic view of the structure of the laminated filter, the MDRO medium pressure reverse osmosis membrane is a core element for separating fresh water and impurities, and is made of a high molecular material, and aromatic polyamide having excellent chemical properties is selected as a material of the laminated membrane. The waste water is pressurized by the water inlet pump to obtain initial pressure, and the waste water enters the high-pressure pump to provide pressure after being filtered by the cartridge filter, the circulating pump provides larger flow to meet the flow speed requirement of an MDRO membrane surface, the liquid circulates in a positive/negative S direction of the laminated flow channel, small molecular particles, dissolved ions and the like in the liquid are intercepted on the concentrated water side, and the permeated fresh water is collected to form clean filtering liquid. The molecular deposition membrane module construction is distinct from a conventional roll-up membrane, the dope flow channel: the disc-tube type membrane component has a patented flow channel design form and adopts an open flow channel. The feed liquid enters the pressure container through the inlet, flows to the other end of the assembly from a channel between the flow guide disc and the shell, and enters the flow guide disc through 8 channels at the flange at the other end, the processed liquid rapidly flows through the filtering membrane at the shortest distance, then reverses to the other membrane surface by 180 degrees, and then flows into the next flow guide disc from the notch at the center of the flow guide disc, so that a double S-shaped route from the periphery of the flow guide disc to the center of the circle, then to the periphery and then to the center of the circle is formed on the surface of the membrane, and finally the concentrated liquid flows out from the flange at the feed end. The distance between the two guide discs of the MDRO component is 3mm, and the surfaces of the guide discs are provided with salient points which are arranged in a certain mode. The special hydraulic design ensures that the treatment fluid flows through the surface of the filter membrane under the action of pressure and forms turbulent flow when meeting the collision of the salient points, thereby increasing the permeation rate and having the self-cleaning function, effectively avoiding the phenomena of membrane blockage and concentration polarization and successfully prolonging the service life of the membrane; the scale on the membrane is easy to clean during cleaning, and the disc-tube membrane group is ensured to be suitable for severe water inlet conditions.

The third-level reverse osmosis membrane blocks all dissolved inorganic molecules and organic matters with the relative molecular mass of more than 100, water molecules can become pure water through the membrane, the removal rate of divalent ions in water can reach 99.5%, and the removal rate of monovalent ions is over 95%. The pure water filtered by the third-level reverse osmosis membrane is clean water which can be recycled and stored in the clear liquid storage barrel 40.

S3, adjusting back the cutting fluid;

it will be appreciated by those skilled in the art that the missing components, typically oils and additives, can be determined by comparing the spent cutting fluid to the virgin cutting fluid in a modest manner, for example, by comparative compositional analysis using HPLC-GC.

S32, detecting the refractive indexes and the densities of the waste cutting fluid and the original cutting fluid by taking the refractive indexes and the densities as actual detection indexes; respectively drawing two influence curves;

s33, collecting and comparing, monitoring the density and the refractive index of the waste cutting fluid in real time, comparing and calculating the density and the refractive index of the waste cutting fluid with those of the original cutting fluid, and calculating the components and the content of the concentrated solution to be added according to the detection result of S32;

specifically, the density and the refractivity of the waste liquid are obtained through real-time monitoring of an online refractometer and an online densimeter, and the amount of the base oil concentrated solution 1 lost in the using process and other high-boiling-point non-evaporated material concentrated solutions 2 (namely additives) added in a fitting manner is automatically calculated.

S34, preparing the lost material into concentrated solutions 1 and 2, automatically adding through a PLC control program, automatically triggering a plurality of external concentrated solution valves by the system, adding corresponding lost concentrated solution from a concentrated solution barrel 50 according to the calculated loss amount, taking the calculated theoretical value A1 as the basis, adding 70% (mass percentage) of the theoretical value A1, detecting the density and the refractive index, obtaining the theoretical value A2 needing to be added after matching with a curve, adding 70% (mass percentage) of the theoretical value A2 again, gradually approaching to the error range that the density and the refractive index are 2% of the initial value, and obtaining the regenerated solution.

In one embodiment, the concentrate is prepared separately for lost oil and additives:

preparing a concentrated solution 1: an oil additive, mineral oil, sebacic acid and oleic acid (in a mass ratio of 10:0.2: 1); the density test result was 0.88 g/ml.

Preparing a concentrated solution 2: low-boiling point volatile substances, triethanolamine, aliphatic polyoxyethylene ether and a bactericide (in a mass ratio of 10:15: 1); the density test result was 1.06 g/ml.

The relationship between the density and the loss ratio of the cutting fluid concentrate is shown in FIG. 4:

the relationship between the refractive index and the loss ratio of the cutting fluid concentrate is shown in FIG. 5:

specific examples the adjusted density was found to be 0.96 g/ml, the refractive index was found to be 0.92, and the loss ratio was found to be 1: 2: 3:1 (by weight) according to the preliminary test.

By combining the test curve of the effect of the concentrated solution on the density, the density of 0.96 g/ml correspondingly loses the concentrated solution 1, and the proportion is 35 percent;

by combining a test curve of the concentrated solution on the influence of the refraction rate, the refractive index of 0.92 corresponds to the loss of the concentrated solution 1, and the proportion is 40 percent;

the system determines that the ratio of concentrate 1 needs to be replenished 35% and the ratio of concentrate 2 is set to 12% in a 3:1 weight ratio system, according to the density priority rule. According to the result, compared with a test curve of the influence of the concentrated solution on the refractive index, the refractive index influence corresponding to the loss of 12% of the concentrated solution 2 is-0.01, and the refractive index influence corresponding to the loss of 35% of the concentrated solution 1 is-0.13, so that the refractive index can be influenced by-0.14 after the concentrated solution is added according to the calculated proportion, and the refractive index of the adjusted cutting fluid is expected to be 1.06. Comparing the test curve of the influence of the concentrated solution on the density, the influence of the 12% concentrated solution loss on the density is-0.01, the influence of the 35% concentrated solution 1 on the density is 0.04, the influence density is 0.03 after the concentrated solution is added according to the calculation proportion, the density of the cutting fluid after adjustment is expected to be 0.93, and the error judgment is in accordance with 2%.

The theoretical amounts of addition a1 were calculated to be 35% for concentrate 1 and 12% for concentrate 2. According to the addition amount of 0.7 × a1, the first addition concentrate 1 was 24.5% and the concentrate 2 was 8.4%. The system automatically detects the density and the refractive index for comparison, obtains the lost quantity of A2, adds the quantity of 0.7 times A2 and repeats until the error value within 2 percent of the initial refractive index and the density is approached finally, and then the system stops.

Water yield of electro-adsorption desalination separation: 70-90%, the power consumption is 0.5-6.0kmh/t, water is produced, the core component is carbon material, the service life is extremely long; the voltage between the polar plates is 0.6-2V, and the salt removing rate is 50-99.5%. See table 1 for comparison of technical parameters of electro-adsorption desalination separation and membrane separation.

TABLE 1

In the specific examples, the components and proportions of the concentrate actually used are as shown in Table 2:

TABLE 2

The technical effects of the invention are tested as follows:

referring to Table 3, the results of the water quality measurements for the run produced water include pH, conductivity, COD, TP, TN, TNi, Cr ⁶⁺ . Therefore, the water quality generated by the electro-adsorption desalination separation in the step S2 is better, and the ionic impurities and the total phosphorus content in the system can be effectively removed (reduced from 35 percent to total phosphorus content)<5%). The recovered water can be returned to a cutting fluid system on line, the water quantity is recovered at a fixed point, and the water is saved.

TABLE 3

Referring to table 4, in order to compare the test results of the new and old cutting fluids, it can be seen that the newly prepared regenerated fluid is comparable to the original fluid in characteristics, each parameter is controllable in performance with the actual use process, and the performance is similar to the original fluid in the life achievement rate of the cutting tool and other reliability tests.

TABLE 4

It should be understood that the exemplary embodiments described herein are illustrative and not restrictive. Although one or more embodiments of the present invention have been described with reference to the accompanying drawings, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.

Claims

1. A method for treating and recycling waste cutting fluid is characterized by comprising the following steps:

s1, pretreatment;

s2, filtering and separating;

s3, adjusting back the cutting fluid;

s31, separating the lost components in the waste cutting fluid into oil and additive,

s33, collecting and comparing, monitoring the density and the refractive index of the waste cutting fluid in real time, comparing and calculating the density and the refractive index of the waste cutting fluid with those of the original cutting fluid, and calculating the lost components and the content of the concentrated solution to be added according to the two influence curves of S32;

2. The method for treating and recycling the waste cutting fluid according to claim 1, wherein the pretreatment in S1 includes oil removal, slag removal, decoloring and sterilization.

3. The method for treating and recycling the waste cutting fluid according to claim 1, wherein the filtering separation in S2 comprises electro-adsorption desalination separation.

4. The method for treating and recycling the waste cutting fluid according to claim 1, wherein the filtering and separating in S2 comprises sequentially performing a primary nano-membrane, a secondary laminated molecular deposition membrane and a tertiary reverse osmosis membrane filtration.

5. The method for treating and recycling the waste cutting fluid as claimed in claim 4, wherein the molecular weight of the organic substances intercepted by the primary nano-membrane is 150-500 g/mol.

6. The method for treating and recycling the waste cutting fluid according to claim 4, wherein the third reverse osmosis membrane blocks dissolved inorganic molecules and organic substances having a relative molecular mass of more than 100 g/mol.

7. The method of claim 1, wherein the filtering and separating in S2 comprises at least one of UF ultrafiltration, electro-adsorption, and electrodialysis.

8. The method for treating and recycling the waste cutting fluid according to claim 1, wherein the filtering separation in S2 comprises at least one of carbon filtration, sand filtration, evaporation from teflon evaporator and low pressure evaporation from MVR.